1. Technical Field
The present invention relates generally to the field of computer systems and, more specifically to computer systems having multiple, logical partitions. Still more particularly, the present invention relates to a logically partitioned computer system, method, and product for booting one of the partitions using one of multiple, different firmware images.
2. Description of Related Art
A logical partitioning option (LPAR) within a data processing system (platform) allows multiple copies of a single operating system (OS) or multiple heterogeneous operating systems to be simultaneously run on a single data processing system hardware platform. A partition, within which an operating system image runs, is assigned a non-overlapping subset of the platform's hardware resources. These platform allocable resources include one or more architecturally distinct processors with their interrupt management area, regions of system memory, and input/output (I/O) adapter bus slots. The partition's resources are represented by its own open firmware device tree to the OS image.
Each distinct OS or image of an OS running within the platform is protected from each other such that software errors on one logical partition can not affect the correct operation of any of the other partitions. This is provided by allocating a disjoint set of platform resources to be directly managed by each OS image and by providing mechanisms for ensuring that the various images can not control any resources that have not been allocated to it. Furthermore, software errors in the control of an operating system's allocated resources are prevented from affecting the resources of any other image. Thus, each image of the OS (or each different OS) directly controls a distinct set of allocable resources within the platform.
Many logically partitioned systems make use of a hypervisor. A hypervisor is a layer of privileged software between the hardware and logical partitions that manages and enforces partition protection boundaries. The hypervisor is also referred to herein as partition management firmware or firmware. The hypervisor is responsible for configuring, servicing, and running multiple logical systems on the same physical hardware. The hypervisor is typically responsible for allocating resources to a partition, installing an operating system in a partition, starting and stopping the operating system in a partition, dumping main storage of a partition, communicating between partitions, and providing other functions. In order to implement these functions, the hypervisor also has to implement its own low level operations like main storage management, synchronization primitives, I/O facilities, heap management, and other functions.
Currently, only a single firmware image can exist within a logically partitioned computer system. This firmware image is used to boot each partition. Each partition, thus, boots from the same image. When the firmware image is modified, the entire boot process must be repeated with each partition being rebooted from the same modified firmware image.
Therefore, a need exists for a logically partitioned system, method, and product for maintaining multiple, different firmware images, and booting only one of the partitions using one of these firmware images, wherein there is no need to reboot the entire system.